The invention relates to a machine that has at least two modes of operation, and more particularly the invention relates to a machine that has at least two modes of operation and the machine includes switching means for changing the machine mode of operation.
Portable machines which include a generator for supplying electric power and a compressor for supplying pressurized fluid are transported on a vehicle such as a truck to a job site where the requisite electrical power and/or compressed fluid are not readily available.
The generator and compressor are driven by a common engine or prime mover. Electrical alternating current (AC) power generators available for use in such portable machines are subject to variations in voltage and frequency as engine speed changes. The change in engine speed is caused by an engine speed regulating system which adjusts the engine speed throttle to match the air compressor power demand. As the compressor power demand decreases, the engine speed is decreased by the throttle. The decrease in prime mover speed is in most applications viewed as an advantage because the decreasing the engine speed results in lower air usage, a savings in fuel consumption, reduction in noise emitted by the machine, and an increase in the machine useful life. However, the engine speed fluctuation is unacceptable for many applications such as fusion welding machines for plastic pipe, which require steady voltage and frequency from the AC power generator, thus requiring steady engine speed.
Running the engine at full speed is an acceptable way to reduce the number of speed variations as the engine is loaded and unloaded by the air compressor and generator demands. However there are a few limitations associated with running the engine at full speed, including increased engine fuel consumption, increased machine noise, and decreased engine life.
Engine governors are often used to maintain engine at constant speed as engine power demand changes. One notable limitation associated with use of engine governors are engine speed overshoot and undershoot from the governed speed as engine power demand is changed suddenly.
Operator training has been used to teach users to avoid using pressurized air during certain applications that require steady generator frequency and voltage. Some limitations associated with this technique include accidental or intentional operation of the service valves, accidental or intentional operation of air driven tools such as jackhammers, and sudden loss of hose integrity due to the activation of hose quick disconnects, cut or damaged hoses.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.